In conventional linear motor systems, a moving element is controlled to move along a track by electromotive force. In a moving magnet linear motor, the moving element typically includes a magnet that holds the moving element to the track. In order to allow movement the moving element generally has bearings which run along the track and is supported by guide rails or the like on the track. The guide rails may engage with the bearings or with the moving element itself. The bearings include plain bearings, ball bearings, needle bearings, roller bearings and the like. In conventional systems, it can be difficult to remove the moving elements from the track either because of the magnetic attraction or because of bearing engagement with the track or guide rails.
In conventional systems, bearings may have specific parallelism tolerances. If the conventional bearings do not meet these tolerances the bearings may be prone to binding during movement.
Conventional bearings are typically not able to move well on curvilinear profiles. While some bearing configurations exist that can move along curved profiles, they are generally costly, difficult to manufacture, and have flexibility constraints with regard to the curvilinear profiles.
Conventional bearings are often preloaded with preloading hardware and have preloading adjustments to ensure the bearings stay in positive contact with the guide rails.
Conventional bearings may have difficulty in achieving high precision, accurate, and repeatable movement along the direction of motion. Factors that may cause variability in precision include i) component manufacturing tolerances, ii) backlash or play, iii) how well the bearings are seated on the guide rail datum surfaces, and iv) the accuracy of the moving element position measuring system. Where backlash or play is the clearance caused by gaps between components or parts.
FIGS. 1, 2, and 3 show example conventional bearing systems. FIG. 1 shows a plain bearing system 10 with a moving element 12 and bearings 14 that are held onto guide rails 16 by the shape of the guide rail 16. FIG. 2 shows a bearing system 20 with a moving element 22 having V wheel bearings 24 held onto guide rails 26. FIG. 3 shows a bearing system 30 with a moving element 32 having recirculating ball bearings 34 held onto guide rails 36. The recirculating ball bearings 34 are around the guide rails 36 and have ball bearings which roll on the guide rails 36. If a moving element on a conventional system were to require inspection, maintenance, or replacement, the conventional guide rails would generally need to be disassembled or opened. The systems 10, 20, 30 may require mechanical disassembly of any of the moving element 12, 22, 32, the bearings 14, 24, 34, and the guide rails 16, 26, 36, in order to remove the moving element 12, 22, 32 from the guide rails 16, 26, 36. The conventional systems in FIGS. 1, 2, and 3 may require preloading or tight manufacturing tolerances on guide rails and bearings to achieve precise movement and positioning. The systems 10, 20, 30 may also be susceptible to binding if the rails are not parallel.